The present disclosure relates to a semiconductor memory device, and more particularly, to a data storage device including a nonvolatile memory device and/or an operating method thereof.
A semiconductor memory device may be volatile or nonvolatile. A volatile semiconductor memory device may support fast read and write speeds, but it loses contents stored therein when powered off. A nonvolatile semiconductor memory device retains contents stored therein, although its power is cut off. The nonvolatile semiconductor memory device, thus, is used to store data to be retained regardless of whether a power is supplied to the nonvolatile semiconductor memory device.
Nonvolatile memory devices may perform an erase operation before a program operation and may not support an overwrite operation. Garbage collection may be performed due to the characteristics of nonvolatile memory devices. The garbage collection may be an operation for generating a free block through the following operations: selecting a victim block, copying valid pages of the victim block into a free block, erasing the victim block, and assigning the erased block to a free block.
Upon performing the garbage collection, a memory block that includes the most number of invalid pages may be selected as a victim block. However, in a three-dimensional nonvolatile memory device, where cell strings are formed in a direction perpendicular to a substrate, various characteristics of a fabrication process makes it difficult to obtain reliability upon storing data. Thus, garbage collection may be executed differently in a three-dimensional nonvolatile memory device.